Polarization insensitive current and magnetic sensors with active temperature compensation

Abstract

This patent document discloses techniques and devices for sensing or measuring electric currents and/or temperature based on photonic sensing techniques. The optical sensors for sensing the current or temperature can be configured as a polarization-insensitive optical sensor in either an optical transmissive configuration or an optical reflective configuration.

What is claimed is: 
     
       1. A current sensor based on optical sensing, comprising:
 a light source that produces probe light; 
 a first fiber line coupled to receive the probe light from the light source and to direct the received probe light along the fiber line; 
 an optical current sensor head coupled to the first fiber line to receive the probe light and configured to include an input polarization prism to separate the received probe light into first and second polarized input beams in different polarizations, a Faraday material located to receive and transmit both the first and second polarized input beams as first and second output beams with rotated polarizations in connection with a magnetic field of a current present near the Faraday material, and an output polarization prism that receives the first and second output beams from the Faraday material and directs the received first and second output beams to merge into an output probe beam carrying information of the current, wherein a polarization direction of the input polarization prism and an polarization direction of the output polarization prism are oriented to be at 45 degrees to each other; and 
 a second fiber line coupled to the optical current sensor head to receive the output probe beam from the output polarization prism; 
 an optical detection unit coupled to the second fiber line to receive the output probe beam from the optical current sensor head; and 
 a measurement module that receives an detector output from the optical detection unit to obtain information of the current. 
 
     
     
       2. The sensor as in  claim 1 , wherein the optical current sensor head includes:
 a first fiber collimator coupled to the first fiber line to receive the probe light and to direct the received probe light to the input polarization prism; and 
 a second fiber collimator coupled to the second fiber line to direct the output probe beam into the second fiber line. 
 
     
     
       3. The sensor as in  claim 1 , comprising:
 an optical power detector coupled to receive a portion of the probe light from the light source to detect a power fluctuation of the probe light, 
 wherein the measurement module that processes the detector output from the optical detector and an output from the optical power detector in obtaining the information of the current. 
 
     
     
       4. A current sensor based on optical sensing, comprising:
 a light source that produces probe light; 
 a first fiber line coupled to receive the probe light from the light source and to direct the received probe light along the fiber line; 
 an optical current sensor head coupled to the first fiber line to receive the probe light and configured to include an input polarization beam displacer made from a birefringent material to transform the received probe light into first and second polarized input beams in different polarizations, a Faraday rotator located to receive and transmit both the first and second polarized input beams with a rotation of 45 degrees in polarization, a Faraday material located to receive and transmit both the first and second polarized input beams from the Faraday rotator as first and second output beams with rotated polarizations in connection with a magnetic field of a current present near the Faraday material, and an output polarization beam displacer made from a birefringent material that receives the first and second output beams from the Faraday material and directs and transforms the received first and second output beams to merge into an output probe beam carrying information of the current; and 
 a second fiber line coupled to the optical current sensor head to receive the output probe beam from the output polarization beam displacer; 
 an optical detection unit coupled to the second fiber line to receive the output probe beam from the optical current sensor head; and 
 a measurement module that receives an detector output from the optical detection unit to obtain information of the current. 
 
     
     
       5. The sensor as in  claim 4 , wherein the optical current sensor head includes:
 a first fiber collimator coupled to the first fiber line to receive the probe light and to direct the received probe light to the input beam displacer; and 
 a second fiber collimator coupled to the second fiber line to direct the output probe beam into the second fiber line. 
 
     
     
       6. The sensor as in  claim 4 , comprising:
 an optical power detector coupled to receive a portion of the probe light from the light source to detect a power fluctuation of the probe light, 
 wherein the measurement module that processes the detector output from the optical detector and an output from the optical power detector in obtaining the information of the current. 
 
     
     
       7. The sensor as in  claim 4 , wherein:
 the Faraday rotator is magnetically shielded from an influence of any external magnetic field. 
 
     
     
       8. A temperature sensor based on optical sensing, comprising:
 a light source that produces probe light; 
 a first fiber line coupled to receive the probe light from the light source and to direct the received probe light along the fiber line; 
 an optical temperature sensor head coupled to the first fiber line to receive the probe light and configured to include an input polarization beam displacer made from a birefringent material to transform the received probe light into first and second polarized input beams in different polarizations, a Faraday rotator that is magnetically shielded from an influence of any external magnetic field and located to receive and transmit both the first and second polarized input beams with a rotation of at or near 45 degrees in polarization as first and second output beams, and an output polarization beam displacer made from a birefringent material that receives the first and second output beams from the Faraday rotator and directs and transform the received first and second output beams to merge into an output probe beam carrying information of the temperature at the Faraday rotator; 
 a second fiber line coupled to the optical temperature sensor head to receive the output probe beam from the output polarization beam displacer; 
 an optical detection unit coupled to the second fiber line to receive the output probe beam from the optical temperature sensor head; and 
 a measurement module that receives an detector output from the optical detection unit to obtain information of the temperature. 
 
     
     
       9. The sensor as in  claim 8 , wherein the optical temperature sensor head includes:
 a first fiber collimator coupled to the first fiber line to receive the probe light and to direct the received probe light to the input beam displacer; and 
 a second fiber collimator coupled to the second fiber line to direct the output probe beam into the second fiber line. 
 
     
     
       10. A current sensor based on optical sensing, comprising:
 a light source that produces probe light; 
 a fiber line coupled to receive the probe light from the light source; 
 an optical current sensor head coupled to the fiber line to receive the probe light and configured to include a polarization beam displacer made from a birefringent material to transform the received probe light into first and second polarized input beams in different polarizations, a Faraday rotator located to receive and transmit both the first and second polarized input beams with a rotation at or near 22.5 degrees in polarization, a Faraday material located to receive and transmit both the first and second polarized input beams from the Faraday rotator with rotated polarizations in connection with a magnetic field of a current present near the Faraday material, and an optical reflector located to receive and reflect the first and second input beams from the Faraday material back to the Faraday material and the Faraday rotator to reach the polarization beam displacer which directs and transforms the received first and second output beams to merge into an output probe beam carrying information of the current; 
 a fiber collimator coupled to the fiber line to direct the probe light from the light source into the polarization beam displacer and to direct the output probe beam from the polarization beam displacer into the fiber line; 
 an optical detection unit coupled to the fiber line to receive the output probe beam from the optical current sensor head; and 
 a measurement module that receives an detector output from the optical detection unit to obtain information of the current. 
 
     
     
       11. The sensor as in  claim 10 , comprising:
 an optical power detector coupled to receive a portion of the probe light from the light source to detect a power fluctuation of the probe light, 
 wherein the measurement module processes the detector output from the optical detector and an output from the optical power detector in obtaining the information of the current. 
 
     
     
       12. A sensor system based on optical sensing, comprising:
 a first fiber link that receives probe light for sensing a temperature at a remote location; 
 a second fiber link that receive probe light for sensing a current at the remote location; and 
 a sensor head at the remote location and including an optical temperature sensor coupled to the first fiber link and an optical current sensor coupled to the second fiber link, 
 wherein the optical temperature sensor is coupled to the fiber line to receive a portion of the probe light and configured to include a polarization prism to separate the received probe light into first and second polarized input beams in different polarizations, a Faraday rotator that is magnetically shielded from an influence of any external magnetic field and located to receive and transmit both the first and second polarized input beams with a rotation of at or near 22.5 degrees in polarization as first and second output beams, and an optical reflector located to receive and reflect the first and second input beams from the Faraday material back to the Faraday material and the Faraday rotator to reach the polarization prism which directs the received first and second output beams to merge into an output probe beam carrying information of the temperature at the Faraday rotator; 
 the optical temperature sensor includes a fiber collimator coupled to the fiber line to direct the probe light from the light source into the polarization prism and to direct the output probe beam from the polarization prism into the fiber line; 
 the optical temperature sensor includes an optical detection unit coupled to the fiber line to receive the output probe beam from the optical temperature sensor head; and 
 the optical temperature sensor includes a measurement module that receives an detector output from the optical detection unit to obtain information of the temperature. 
 
     
     
       13. The system as in  claim 12 , comprising:
 a first light source that produces the probe light in the first fiber link; and 
 a second light source that produces the probe light in the second fiber link. 
 
     
     
       14. The system as in  claim 12 , comprising:
 a single light source that produces the probe light in the first and second fiber links; and 
 an optical splitter that splits the probe light from the single light source into a first probe beam coupled into the first fiber link and a second probe beam coupled into the second fiber link. 
 
     
     
       15. A sensor system based on optical sensing, comprising:
 a first fiber link that receives probe light for sensing a temperature at a remote location; 
 a second fiber link that receive probe light for sensing a current at the remote location; and 
 a sensor head at the remote location and including an optical temperature sensor coupled to the first fiber link and an optical current sensor coupled to the second fiber link, 
 wherein the optical current sensor is coupled to the fiber line to receive a portion of the probe light and configured to include a polarization prism to separate the received probe light into first and second polarized input beams in different polarizations, a Faraday rotator located to receive and transmit both the first and second polarized input beams with a rotation at or near 22.5 degrees in polarization, a Faraday material located to receive and transmit both the first and second polarized input beams from the Faraday rotator with rotated polarizations in connection with a magnetic field of a current present near the Faraday material, and an optical reflector located to receive and reflect the first and second input beams from the Faraday material back to the Faraday material and the Faraday rotator to reach the polarization prism which directs the received first and second output beams to merge into an output probe beam carrying information of the current; 
 the optical current sensor includes a fiber collimator coupled to the fiber line to direct the probe light from the light source into the polarization prism and to direct the output probe beam from the polarization prism into the fiber line; 
 the optical current sensor includes an optical detection unit coupled to the fiber line to receive the output probe beam from the optical current sensor head; and 
 the optical current sensor includes a measurement module that receives an detector output from the optical detection unit to obtain information of the current. 
 
     
     
       16. The system as in  claim 15 , comprising:
 a first light source that produces the probe light in the first fiber link; and 
 a second light source that produces the probe light in the second fiber link. 
 
     
     
       17. The system as in  claim 15 , comprising:
 a single light source that produces the probe light in the first and second fiber links; and 
 an optical splitter that splits the probe light from the single light source into a first probe beam coupled into the first fiber link and a second probe beam coupled into the second fiber link. 
 
     
     
       18. A current sensor based on optical sensing and temperature compensation, comprising:
 a fiber line coupled to receive probe light containing light at first and second optical wavelengths; 
 an optical current sensor head coupled to the fiber line to receive the probe light and configured to include a polarization beam displacer made from a birefringent material to transform the received probe light into first and second polarized input beams in different polarizations, a Faraday rotator which is magnetically shielded from an external magnetic field and located to receive the first and second polarized input beams to cause a rotation in polarization, a dichroic filter located downstream from the Faraday rotator to receive light from the Faraday rotator and configured to transmit light at the first optical wavelength and reflect light at the second optical wavelength, a sensing Faraday material that is not magnetically shielded and placed in an optical path of light transmitted by the dichroic filter to sense a polarization rotation in light at the second optical wavelength caused by a temperature change and a magnetic field of an electric current at or near the sensing Faraday material, and an optical reflector downstream from the sensing Faraday material to reflect the light at the second optical wavelength back to the sensing Faraday material, the dichroic filter and the Faraday rotator to return to the polarization beam displacer and the fiber line along with the reflected light at the first optical wavelength; 
 a first optical detector coupled to receive reflected light from the fiber line at the first optical wavelength that carries information of the current to be measured and an influence of a temperature at the optical current sensor head; 
 a second optical detector coupled to receive reflected light from the fiber line at the second optical wavelength that carries information of the temperature at the Faraday rotator; and 
 a measurement module that receives detector outputs from the first and second optical detectors to obtain information of the current to be measured and to compensate for an effect to the current measurement by the temperature. 
 
     
     
       19. The sensor as in  claim 18 , comprising:
 a first light source that generates the probe light at the first optical wavelength; and 
 a second light source that generates the probe light at the second optical wavelength. 
 
     
     
       20. The sensor as in  claim 18 , comprising:
 a single light source that generates the probe light at the first optical wavelength and at the second optical wavelength, 
 wherein the probe light is coupled into the fiber line. 
 
     
     
       21. The sensor as in  claim 20 , comprising:
 a fiber coupler coupled to the fiber line to split a portion of the probe light from the light source as a power monitor signal beam, and to split a portion of the reflected light from the optical current sensor head as a signal beam; 
 an optical splitter coupled to receive the signal beam containing light at the first and second optical wavelengths and to output a first signal beam at the first optical wavelength to the first optical detector and a second signal beam at the second optical wavelength to the second optical detector; 
 an optical power monitor detector coupled to receive the power monitor signal beam from the fiber coupler; and 
 wherein the measurement module that receives detector outputs from the first and second optical detectors and the optical power monitor detector to obtain information of the current to be measured and to compensate for effects to the current measurement by the temperature and by power fluctuation in the light source. 
 
     
     
       22. The sensor as in  claim 20 , wherein:
 the Faraday rotator is configures to cause a rotation at or near 22.5 degrees in polarization. 
 
     
     
       23. A current sensor based on optical sensing and temperature compensation, comprising:
 a fiber line coupled to receive probe light containing light at first and second optical wavelengths; 
 an optical current sensor head coupled to the fiber line to receive the probe light and configured to include a polarization prism to separate the received probe light into first and second polarized input beams in different polarizations, a Faraday rotator which is magnetically shielded from an external magnetic field and located to receive the first and second polarized input beams to cause a rotation in polarization, a dichroic filter located downstream from the Faraday rotator to receive light from the Faraday rotator and configured to transmit light at the first optical wavelength and reflect light at the second optical wavelength, a sensing Faraday material that is not magnetically shielded and placed in an optical path of light transmitted by the dichroic filter to sense a polarization rotation in light at the second optical wavelength caused by a temperature change and a magnetic field of an electric current at or near the sensing Faraday material, and an optical reflector downstream from the sensing Faraday material to reflect the light at the second optical wavelength back to the sensing Faraday material, the dichroic filter and the Faraday rotator to return to the polarization prism and the fiber line along with the reflected light at the first optical wavelength; 
 a first optical detector coupled to receive reflected light from the fiber line at the first optical wavelength that carries information of the current to be measured and an influence of a temperature at the optical current sensor head; 
 a second optical detector coupled to receive reflected light from the fiber line at the second optical wavelength that carries information of the temperature at the Faraday rotator; 
 a measurement module that receives detector outputs from the first and second optical detectors to obtain information of the current to be measured and to compensate for an effect to the current measurement by the temperature; 
 a single light source that generates the probe light at the first optical wavelength and at the second optical wavelength, wherein the probe light is coupled into the fiber line; 
 a first fiber coupler coupled to the fiber line to split a portion of the probe light from the light source as a first power monitor signal beam, and to split a portion of the reflected light from the optical current sensor head as a first signal beam to the first optical detector; 
 a second fiber coupler coupled to the fiber line to split a portion of the probe light from the light source as a second power monitor signal beam, and to split a portion of the reflected light from the optical current sensor head as a second signal beam to the second optical detector; 
 a first optical bandpass filter placed in front of the first optical detector to transmit light at the first optical wavelength into the first optical detector; 
 a second optical bandpass filter placed in front of the second optical detector to transmit light at the second optical wavelength into the second optical detector; 
 a first optical power monitor detector coupled to receive the first power monitor signal beam from the first fiber coupler; 
 a third optical bandpass filter placed in front of the first optical power monitor detector to transmit light at the first optical wavelength into the first optical power monitor detector; 
 a second optical power monitor detector coupled to receive the second power monitor signal beam from the second fiber coupler; 
 a fourth optical bandpass filter placed in front of the second optical power monitor detector to transmit light at the second optical wavelength into the second optical power monitor detector; and 
 wherein the measurement module that receives detector outputs from the first and second optical detectors and the first and second optical power monitor detectors to obtain information of the current to be measured and to compensate for effects to the current measurement by the temperature and by power fluctuations at the first and second optical wavelengths in the light source. 
 
     
     
       24. A current sensor based on optical sensing and temperature compensation, comprising:
 a fiber line coupled to receive probe light containing light at first and second optical wavelengths; 
 an optical current sensor head coupled to the fiber line to receive the probe light and configured to include a polarization prism to separate the received probe light into first and second polarized input beams in different polarizations, a Faraday rotator which is magnetically shielded from an external magnetic field and located to receive the first and second polarized input beams to cause a rotation in polarization, a dichroic filter located downstream from the Faraday rotator to receive light from the Faraday rotator and configured to transmit light at the first optical wavelength and reflect light at the second optical wavelength, a sensing Faraday material that is not magnetically shielded and placed in an optical path of light transmitted by the dichroic filter to sense a polarization rotation in light at the second optical wavelength caused by a temperature change and a magnetic field of an electric current at or near the sensing Faraday material, and an optical reflector downstream from the sensing Faraday material to reflect the light at the second optical wavelength back to the sensing Faraday material, the dichroic filter and the Faraday rotator to return to the polarization prism and the fiber line along with the reflected light at the first optical wavelength; 
 a first optical detector coupled to receive reflected light from the fiber line at the first optical wavelength that carries information of the current to be measured and an influence of a temperature at the optical current sensor head; 
 a second optical detector coupled to receive reflected light from the fiber line at the second optical wavelength that carries information of the temperature at the Faraday rotator; 
 a measurement module that receives detector outputs from the first and second optical detectors to obtain information of the current to be measured and to compensate for an effect to the current measurement by the temperature; 
 a single light source that generates the probe light at the first optical wavelength and at the second optical wavelength, wherein the probe light is coupled into the fiber line; 
 a fiber coupler coupled to the fiber line to split a portion of the probe light from the light source as a power monitor signal beam, and to split a portion of the reflected light from the optical current sensor head as a signal beam; 
 a first optical splitter coupled to receive the signal beam containing light at the first and second optical wavelengths and to output a first signal beam at the first optical wavelength to the first optical detector and a second signal beam at the second optical wavelength to the second optical detector; 
 a second optical splitter coupled to receive the power monitor signal beam containing light at the first and second optical wavelengths and to output a first power monitor signal beam at the first optical wavelength and a second power monitor signal beam at the second optical wavelength; 
 a first optical power monitor detector coupled to receive the first power monitor signal beam from the second fiber coupler; and 
 a second optical power monitor detector coupled to receive the second power monitor signal beam from the second fiber coupler; 
 wherein the measurement module that receives detector outputs from the first and second optical detectors and the first and second optical power monitor detectors to obtain information of the current to be measured and to compensate for effects to the current measurement by the temperature and by power fluctuations at the first and second optical wavelengths in the light source. 
 
     
     
       25. A current sensor based on optical sensing and temperature compensation, comprising:
 a fiber line coupled to receive probe light containing light at first and second optical wavelengths; 
 an optical current sensor head coupled to the fiber line to receive the probe light and configured to include a polarization prism to separate the received probe light into first and second polarized input beams in different polarizations, a Faraday rotator which is magnetically shielded from an external magnetic field and located to receive the first and second polarized input beams to cause a rotation in polarization, a dichroic filter located downstream from the Faraday rotator to receive light from the Faraday rotator and configured to transmit light at the first optical wavelength and reflect light at the second optical wavelength, a sensing Faraday material that is not magnetically shielded and placed in an optical path of light transmitted by the dichroic filter to sense a polarization rotation in light at the second optical wavelength caused by a temperature change and a magnetic field of an electric current at or near the sensing Faraday material, and an optical reflector downstream from the sensing Faraday material to reflect the light at the second optical wavelength back to the sensing Faraday material, the dichroic filter and the Faraday rotator to return to the polarization prism and the fiber line along with the reflected light at the first optical wavelength; 
 a first optical detector coupled to receive reflected light from the fiber line at the first optical wavelength that carries information of the current to be measured and an influence of a temperature at the optical current sensor head; 
 a second optical detector coupled to receive reflected light from the fiber line at the second optical wavelength that carries information of the temperature at the Faraday rotator; 
 a measurement module that receives detector outputs from the first and second optical detectors to obtain information of the current to be measured and to compensate for an effect to the current measurement by the temperature; 
 a single light source that generates the probe light at the first optical wavelength and at the second optical wavelength, wherein the probe light is coupled into the fiber line; and 
 an optical monitor module coupled to the fiber link that includes the first and second optical detectors and further includes: 
 a first optical coupler coupled to receive the probe light containing light at the first and second optical wavelengths from the light source and to output a first signal beam at the first optical wavelength along a first optical path and a second signal beam at the second optical wavelength along a second optical path; 
 a second optical coupler coupled to the first and second optical paths to combine the light at the first and second optical wavelengths into a combined optical beam and further coupled to the fiber link to direct the combined optical beam into the fiber link to the optical current sensor head and to split the reflected light into a first reflected light beam at the first optical wavelength along the first optical path and a second reflected light beam at the second optical wavelength along the second optical path; 
 a third optical coupler coupled to the first optical path to split a portion of the first signal beam at the first optical wavelength as a first power monitor signal beam at the first optical wavelength and to split a portion of the first reflected light beam at the first optical wavelength as a first signal beam at the first optical wavelength into the first optical detector; 
 a first optical power monitor detector coupled to receive the first power monitor signal beam from the third optical coupler; 
 a fourth optical coupler coupled to the second optical path to split a portion of the second signal beam at the second optical wavelength as a second power monitor signal beam at the second optical wavelength and to split a portion of the second reflected light beam at the second optical wavelength as a second signal beam at the second optical wavelength into the second optical detector; and 
 a second optical power monitor detector coupled to receive the second power monitor signal beam from the fourth optical coupler; 
 wherein the measurement module that receives detector outputs from the first and second optical detectors and the first and second optical power monitor detectors to obtain information of the current to be measured and to compensate for effects to the current measurement by the temperature and by power fluctuations at the first and second optical wavelengths in the light source.